You can get highlight event in your main application when a new highlight is added, removed or modified. the data in the highlight is received as Highlight and its respective action as HighlightAction

folioReader.setOnHighlightListener(new OnHighlightListener() {
    @Override
    public void onHighlight(HighLight highlight, HighLight.HighLightAction type) {
        // Do something with the received highlight
    }
);

Once done with folioReader object don't forget to call static method clear() of FolioReader class -

Folioreader.clear();